There is a strong need in drug discovery for cellular assays that better predict human responses to drugs. A key technical hurdle has been the difficulty of incorporating complex tissue architecture and cellular microenvironments into an assay format that is compatible with the high throughput approaches used for early drug discovery. In this proposal we propose to develop and commercialize a Microfluidic Reconstituted Tissue Device ([unreadable]F-RTD) that will enable more physiologically relevant cellular assays in a high throughput, automated format. The device is a tubeless, automatable array of microfluidic channels for co-culture of mammalian cells in adjacent compartments in a three-dimensional format. The unique liquid flow properties at the microscale enable the construction of a robust, highly reproducible two-compartment tissue model in a highly parallel fashion. This means that potential drug molecules can be tested for their effects on disease processes in the context of intact tissue as opposed to non-physiological monolayers of cells. In Phase I, we developed a prototype microfluidic device and used it to extend a well established model of mammary epithelial acinar morphogenesis into a two compartment tissue model including fibroblasts. We will use this mammary tissue model to establish the design parameters of the [unreadable]F-RTD and to functionally validate it for robust high throughput tumorigenesis assays. Prototype devices will be fabricated from elastomeric polymer and optimized designs will be fabricated from polystyrene. The plastic [unreadable]F-RTD devices will be validated using assays for key tumorigenic processes, including cell proliferation, apoptosis, and invasion using mammary epithelial and stromal cell lines as well as primary cells. In situ immunocytochemistry methods and fluorescent imaging will be the key methods used for analysis. Finally, the [unreadable]F-RTD will be fully validated for high throughput screening and drug discovery by optimizing its integration with standard automated liquid dispensing equipment. Cellular assays that are more predictive are greatly needed in the pharmaceutical industry to improve the success rate in clinical trials, and in biomedical research in general to increase our understanding of disease mechanisms. In this proposal we plan to develop and commercialize a Microfluidic Reconstituted Tissue Device that will enable more physiologically relevant cellular assays in a high throughput, automated format. [unreadable] [unreadable] [unreadable]